Adipic acid, polymerization

Chemical Composition. In polyamide 6 (PA 6, polymerization product of e-caprolactam) and polyamide 66 (PA 66, adipic acid polymerized with hexamethylene-diamine) one chain end consists of an amino group, which can be present in the free state or in the acylated form. Amino groups are of special importance for dyeing because they form ammonium groups in an acidic dyebath by addition of protons. The lower dye uptake in comparison to wool is caused by the comparatively low number of amino groups. The depth of color achieved on PA 6 is somewhat less than that on PA 66. 

Nylon A class of synthetic fibres and plastics, polyamides. Manufactured by condensation polymerization of ct, oj-aminomonocarboxylic acids or of aliphatic diamines with aliphatic dicarboxylic acids. Also rormed specifically, e.g. from caprolactam. The different Nylons are identified by reference to the carbon numbers of the diacid and diamine (e.g. Nylon 66 is from hexamethylene diamine and adipic acid). Thermoplastic materials with high m.p., insolubility, toughness, impact resistance, low friction. Used in monofilaments, textiles, cables, insulation and in packing materials. U.S. production 1983 11 megatonnes. 

Figure 5.3 shows the data for the uncatalyzed polymerization of adipic acid and 1,10-decamethylene glycol at 161°C plotted according to Eq. (5.21). The various provisos of the catalyzed case apply here also, so it continues to be appropriate to consider only the final stages of the conversion to polymer. From these results, k is about 4.3 X 10" kg eq min at 161°C. 

Polymerization of AA and BB monomers is illustrated by butane-1,4-diol and adipic acid. The aabb repeat unit in the polymer has an Mq value of 200. If Eq. (5.4) is used to evaluate it gives the number of aa plus bb units therefore = 200(hj )/2. 

As an example of the quantitative testing of Eq. (5.47), consider the polymerization of diethylene glycol (BB) with adipic acid (AA) in the presence of 1,2,3-propane tricarboxylic acid (A3). The critical value of the branching coefficient is 0.50 for this system by Eq. (5.46). For an experiment in which r = 0.800 and p = 0.375, p = 0.953 by Eq. (5.47). The critical extent of reaction, determined by titration, in the polymerizing mixture at the point where bubbles fail to rise through it was found experimentally to be 0.9907. Calculating back from Eq. (5.45), the experimental value of p, is consistent with the value =0.578. 

Adipic acid undergoes the usual reactions of carboxyflc acids, including esterification, amidation, reduction, halogenation, salt formation, and dehydration. Because of its biflmctional nature, it also undergoes several industrially significant polymerization reactions. 

Amidation. Heating of the diammonium salt or reaction of the dimethyl ester with concentrated ammonium hydroxide gives adipamide [628-94-4] mp 228°C, which is relatively insoluble in cold water. Substituted amides are readily formed when amines are used. The most industrially significant reaction of adipic acid is its reaction with diamines, specifically 1,6-hexanediamine. A water-soluble polymeric salt is formed initially upon mixing solutions of the two materials then hea ting with removal of water produces the polyamide, nylon-6,6. This reaction has been studied extensively, and the hterature contains hundreds of references to it and to polyamide product properties (31). 

Ingredients. Nylon-6,6 is made from the reaction of adipic acid [124-04-9] and hexamethylenediamine [124-09-4]. The manufacture of intermediates for polyamides is extremely important not only is the quaUty of the polymer, such as color, degree of polymerization, and linearity, strongly dependent on the ingredient quaUty, but also the economic success of the producer is often determined by the yields and cost of manufacture of the ingredients. 

Braided Synthetic Nonabsorbable Sutures. Braided synthetic nonabsorbable sutures are made by melt-spinning thermoplastic polymers into fine filaments (yams), and braiding them, with or without a core, to form multifilament sutures in a range of sizes. Nylon-6,6 [32131 -17-2] (7) is a polyamide produced by the condensation polymerization of adipic acid and 1,6-hexanediamine. 

The diacids are characterized by two carboxyHc acid groups attached to a linear or branched hydrocarbon chain. AUphatic, linear dicarboxyhc acids of the general formula HOOC(CH2) COOH, and branched dicarboxyhc acids are the subject of this article. The more common aUphatic diacids (oxaUc, malonic, succinic, and adipic) as weU as the common unsaturated diacids (maleic acid, fumaric acid), the dimer acids (qv), and the aromatic diacids (phthaUc acids) are not discussed here (see Adipic acid Maleic anhydride, maleic acid, and fumaric acid Malonic acid and derivatives Oxalic acid Phthalic acid and OTHERBENZENE-POLYCARBOXYLIC ACIDS SucciNic ACID AND SUCCINIC ANHYDRIDE). The bihinctionahty of the diacids makes them versatile materials, ideally suited for a variety of condensation polymerization reactions. Several diacids are commercially important chemicals that are produced in multimillion kg quantities and find appHcation in a myriad of uses. 

Butadiene is by far the most important monomer for synthetic rubber production. It can be polymerized to polybutadiene or copolymerized with styrene to styrene-butadiene rubber (SBR). Butadiene is an important intermediate for the synthesis of many chemicals such as hexa-methylenediamine and adipic acid. Both are monomers for producing nylon. Chloroprene is another butadiene derivative for the synthesis of neoprene rubber. 

Nylon 66 is produced by the reaction of hexamethylenediamine and adipic acid (see Chapters 9 and 10 for the production of the two monomers). This produces hexamethylenediammonium adipate salt. The product is a dilute salt solution concentrated to approximately 60% and charged with acetic acid to a reactor where water is continuously removed. The presence of a small amount of acetic acid limits the degree of polymerization to the desired level ... 

PA-6,6 is made from the relatively expensive materials hexamethylene diamine and adipic acid. An alternative synthesis of PA-6,6 from adiponitrile and hexamethylene diamine utilizing water is under investigation.16 PA-6 can be synthesized in a continuous process at atmospheric pressure, but reaction times are very long as the ring-opening initiation step is particularly slow. The reaction time can be shortened considerably by carrying out prepolymerization in the presence of excess water at pressure however, this makes the continuous polymerization process more complex. Copolymers with amide units of uniform length (diamides) are relatively new the diamide units are able to crystallize easily and have a thermally stable crystalline structure. 

To reduce the chance of side reactions, such as the dimerization of the diamine to tUjtw -diaminodihexylamine in (3.17) and the degradation of adipic acid to Schiff bases in (3.16), the precondensation can be carried out either for 30-60 min below 250°C or very rapidly (seconds) at 250-290°C. In the (pre)polymerization step, a concentrated PA salt solution is pumped into a set of heating tubes. These tubes have several heating zones as their diameter gradually increases in size.5,6,28... 

In 1930, DuPont launched the synthetic fiber industry with the discovery of nylon-6,6.2 In 1938, a pilot plant for nylon-6,6 production was put into operation, and in 1939, production was commenced at a large-scale plant in Seaford, Delaware. The classical method for the synthesis of nylon-6,6 involves a two-step process. In the first step, hexamethylene diamine (HMDA) is reacted with adipic acid (AA) to form a nylon salt. Polymerization of the aqueous salt solution is carried out at temperatures in the range of about 210-275°C at a steam pressure of about 1.7 MPa. When 275°C is reached, the pressure is reduced to atmospheric pressure and heating is continued to drive the reaction to completion. 

Waste nylon-6,6 was washed in a diluted commercial detergent solution at 100°C for 0.5 h and then rinsed twice with water to remove any finishes present. The washed nylon-6,6 was then reacted with molten adipic acid for 1.5 h or more at a temperature of 175°C with a weight ratio of nylon-to-adipic acid of 0.15 1. The molten product was then exposed to steam at a temperature of 230-233°C to remove any stabilizers present. The acidolysis product was then hydrolyzed with water at a temperature of 204°C under autogenous pressure for 0.5 h or longer with a ratio of water to acidolysis product of 0.50 1 (w/w). The hot solution was then filtered at 100°C to remove any titanium dioxide present. The filtered product was then mixed with HMDA to neutralize any excess acid present. The solution was then filtered to remove any solids. A 50% by weight aqueous solution of HMDA was added to the filtrate, and under standard polymerization conditions, polyhexamethylene adipamide (nylon-6,6) was produced. 

Condensation polymerization of amines with carboxylic acids leads to the polyamides, substances more commonly known as nylons. A common polyamide is nylon-66, which is a polymer of 1,6-diaminohexane, H2N(GH2)6NH2, and adipic acid, HOOC(CH2)4COOH. The 66 in the name indicates the numbers of carbon atoms in the two monomers. 

Nylon 66 is a condensation polymer made from adipic acid and iiexamethylenediamine. Nylon 6 is made by ring-opening polymerization of caprolactam. 

Most of the hexamethylenediamine produced is used for the manufacture of Type 66 nylon by polymerization with adipic acid. A minor use is for the preparation of hexamethylene diisocyanate used in light-stable polyurethane coatings. 

The effects of the feed ratio in the lipase CA-catalyzed polymerization of adipic acid and 1,6-hexanediol were examined by using NMR and MALDI-TOF mass spectroscopies. NMR analysis showed that the hydroxyl terminated product was preferentially formed at the early stage of the polymerization in the stoichiometric substrates. As the reaction proceeded, the carboxyl-terminated product was mainly formed. Even in the use of an excess of the dicarboxylic acid monomer, the hydroxy-terminated polymer was predominantly formed at the early reaction stage, which is a specific polymerization behavior due to the unique enzyme catalysis. 

Divinyl esters reported first by us are efficient monomers for polyester production under mild reaction conditions. In the lipase PF-catalyzed polymerization of divinyl adipate and 1,4-butanediol in diisopropyl ether at 45°C, a polyester with molecular weight of 6.7 x 10 was formed, whereas adipic acid and diethyl adipate did not afford the polymeric materials under similar reaction conditions (Scheme 3). 

A process for the hydrogenation of adiponitrile and 6-aminocapronitrile to hexamethylenediamine in streams of depolymerized Nylon-6,6 or a blend of Nylon-6 and Nylon-6,6 has been described. Semi-batch and continuous hydrogenation reactions of depolymerized (ammonolysis) products were performed to study the efficacy of Raney Ni 2400 and Raney Co 2724 catalysts. The study showed signs of deactivation of Raney Ni 2400 even in the presence of caustic, whereas little or no deactivation of Raney Co 2724 was observed for the hydrogenation of the ammonolysis product. The hydrogenation products from the continuous run using Raney Co 2724 were subsequently distilled and the recycled hexamethylenediamine (HMD) monomer was polymerized with adipic acid. The properties of the polymer prepared from recycled HMD were found to be identical to that obtained from virgin HMD. 

The hydrogenation products from the continuous run using Raney Co 2724 were subsequently distilled and the product hexamethylenediamine monomer (i.e. recycled HMD ) was polymerized with adipic acid. The properties of the polymer prepared from recycled HMD were found to be identical to that obtained from virgin HMD, indicating that the continuous hydrogenation of ammonolysis product offers potential for the commercial production of recycled Nylon. 

The nylon 66 molecule shown in Fig, 1,11 is a thermoplastic polymer, created by the step growth polymerization of hexamine and adipic acid. The majority of commercial polymers are thermoplastics, which permits us to readily mold them to many useful shapes. 

The nomenclature of nylon is based on the number of carbon atoms found in the monomers. Thus, caprolactam, which contains six carbon atoms per molecule is polymerized to form nylon 6. Nylon 46 (pronounced "nylon four six ) is made from 1,4 diaminobutane, which contains four carbon atoms and adipic acid which contains six carbon atoms. The convention that we use to name nylons is summarized in Fig. 23.4. 

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